Image guided medical and surgical procedures utilize patient images obtained prior to or during a medical procedure to guide a physician performing the procedure. Recent advances in imaging technology, especially in imaging technologies that produce highly-detailed, computer-generated two, three and four-dimensional images, such as computed tomography (CT), magnetic resonance imaging (MRI), isocentric C-arm fluoroscopic imaging, fluoroscopes or ultrasounds have increased the interest in image guided medical procedures. Various imaging devices may include imaging devices such as an O-arm including those disclosed in U.S. Patent Application Publication 2004/0022350, entitled “Breakable Gantry Apparatus for Multidimensional X-Ray Based Imaging”; U.S. Patent Application Publication 2004/0013239, entitled “Systems and Methods for Quasi-Simultaneous Multi-Planar X-Ray Imaging”; U.S. Patent Application Publication 2004/0013225, entitled “Systems and Methods for Imaging Large Field-of-View Objects”; U.S. Patent Application Publication 2003/0235266, entitled “Cantilevered Gantry Apparatus for X-Ray Imaging”, each of which is incorporated herein by reference. Furthermore, various other imaging apparatus may include a O-arm apparatus such as those disclosed in U.S. Patent Application Publication 2003/0072416, entitled “Interventional Volume Scanner” and U.S. Pat. No. 6,203,196, entitled “X-Ray Diagnostic Apparatus with a Beam Transmitter and a Beam Receiver Mounted Opposite One Another on a Curved Holder”; each of which is incorporated herein by reference.
During these image guided medical procedures, the area of interest of the patient that has been imaged is displayed on a display. Surgical instruments and/or implants that are used during this medical procedure are tracked and superimposed onto this display to show the location of the surgical instrument relative to the area of interest in the body. Other types of navigation systems operate as an image-less system, where an image of the body is not captured by an imaging device prior to the medical procedure, such as the device disclosed in U.S. patent application Ser. No. 10/687,539, entitled Method And Apparatus For Surgical Navigation Of A Multiple Piece Construct For Implantation, filed Oct. 16, 2003, which is incorporated herein by reference. With this type of procedure, the system may use a probe to contact certain landmarks in the body, such as landmarks on bone, where the system generates either a two-dimensional or three-dimensional model of the area of interest based upon these contacts. This way, when the surgical instrument or other object is tracked relative to this area, they can be superimposed on this model.
Most types of orthopedic medical procedures are performed using conventional surgical techniques that are performed on various parts of the body, such as spine, hip, knee, shoulder, a synovial joint, and a facet joint. These techniques generally involve opening the patient in a relatively invasive manner to provide adequate viewing by the surgeon during the medical procedure. These types of procedures, however, generally extend the recovery period for the patient due to the extent of soft tissue and muscular incisions resulting from the medical procedure. Use of image guided technology in orthopedic medical procedures would enable a more minimally invasive type of procedure to be performed to thereby reduce the overall recovery time and cost of the procedure. Use of the image guided procedure may also enable more precise and accurate placement of an implant within the patient.
The implantation of disc prostheses is an emerging surgical procedure. In order for the disc prosthesis to be optimally functional, it must be placed directly in the disc space between two vertebral bodies. Typically, this position is in the anatomical midline of the spine (i.e., mid-sagittal plane), parallel to the respective vertebral body end plates, with the center of rotation of the disc prosthesis at the center of rotation of the two vertebral bodies. The center of rotation is typically positioned or located at the posterior one-third of the disc space.
However, this type of implant procedure is currently performed using a C-arm fluoroscope to assist the surgeon with placing and aligning the disc prosthesis. During the surgery, the surgeon must judge the mid-line and center of rotation by interpreting images generated from the C-arm. To judge the mid-line, the surgeon or possibly the C-arm operator manipulates the C-arm in the A-P plane, such that a true A-P images is generated, which is generally defined as the spinous process of the vertebral body that equally bisects the two pedicles of the same vertebral body. Once the image is generated, the surgeon will mark the mid-line of the spine, and often place a marker, such as a screw in adjacent vertebral bodies to help guide the placement of the implant. When the disc prosthesis is placed, the surgeon uses these marks to help judge and correct mid-line placement. However, this is time consuming and a tedious step that may not be followed precisely and possibly lead to misplacement of the implant. Moreover, the anterior mid-line mark only denotes the mid-line starting point and does not dictate the mid-line trajectory (i.e. mid-sagittal plane). This trajectory is ultimately left to the skill of the surgeon to determine the final implant trajectory, which is subject to a great amount of variability from surgeon-to-surgeon.
To judge the placement of the disc prosthesis with respect to the center of rotation of vertebral bodies, the C-arm is aligned laterally and fluoroscopic images are obtained during insertion. Once again, the surgeon must use judgment to determine when the disc prosthesis has been inserted posteriorly enough. There are currently no tools available to assist in this judgment available today. Moreover, by requiring the surgeon to take multiple fluoroscopic images, this exposes both the patient and the surgical team to potential undesirable exposure from the fluoroscope. It also requires and takes a significant amount of time to take and analyze these fluoroscopic images, thereby extending the length of the surgical procedure.
Therefore, it is desired to provide a system that allows for substantial navigation and tracking of a prosthesis relative to a portion of the anatomy to ensure that the prosthesis is positioned in a selected portion of the anatomy and a proper orientation, position, and the like, without relying substantially solely on a user's judgment and reducing the number of images required to be taken of a patient.